But your metabolism is supercharged and burning more calories.
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jmort253Mar 8 '11 at 4:17

5

+1 for metabolism increases for the rest of the day. I've found that if I work out too late I'm too amped to get to sleep at night.
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Evan PlaiceMar 20 '11 at 20:30

As a kid I did a fair amount of competitve swimming, I would go to training sessions before school. I swear I learnt more at school on those days.
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StephenPaulgerMar 24 '11 at 0:01

On the other hand you're dehydrated and that's not even good for your joints / spine. I got these problems so I keep an eye out for these things. Getting hydrated takes time, about 4 hours.
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LorenzoFeb 29 '12 at 23:05

Generally, I don't think it really matters for your metabolism when you start working out. There are no golden rules, because some people are night owls and others are early birds. Furthermore, you can habituate your body to a certain rhythm, so pick what suits you best and your body will probably adapt to it.

In general you should try to workout not right after eating, so that means getting up early to do it before breakfast or just before dinner. If all else fails, you generally will have to wait until a couple hours after dinner before you can get going.

So, I'd say the two most important factors are your sleeping and eating habits and of less importance, your working schedule which could dictate when you have the time.

For weight loss, all that matters is the calorie deficit. You can lose weight just by reducing caloric intake and without exercising. *Of course, exercising can help you lose weight faster because a pound of muscle burns more calories than a pound of fat (a help of maybe about -6 calories/day for us non-Olympic athletes - it's still help!).

When to exercise is a personal thing. Some people like to avoid a crowded gym so they go on "off-hours". Some people like having someone to talk to, so they go during "peak" hours. Some people don't want to shower at the gym so they'll work out after work and shower when they get home.

Don't feel like you have to lock into a routine (always morning, noon, or night), life happens. You might get discouraged if an emergency lunch meeting derails your gym plans and you feel like you've "failed".

A lot of people's AM is more routine than their afternoons. If you work out before you start your day, you're less apt to have something get in the way of your workout, and less apt to find an excuse. Also, the gym is way less crowded in the morning.

If you're talking about cardio, there are a few reasons to do it first thing in the morning.

First of all, you haven't eaten for several hours, so your body will turn to fat for energy instead of food you've eaten. According to this post,

you wake up in the morning with depleted glycogen and lower blood
sugar - the optimum environment for burning fat instead of
carbohydrate. How much more fat you'll burn is uncertain, but some
studies have suggested that up to 300% more fat is burned when cardio
is done in a fasted, glycogen-depleted state.

Additionally, exercising in the morning gives your body the most amount of time to take advantage of the "after burn" effect. Your metabolism increases after you work out, and while this is true no matter what time you work out, it's also true that your metabolism slows when you go to sleep. So, if you exercise closer to bed, you won't get as much of this particular benefit.

I recognise the benefits of morning workout (before breakfast). But it involves for most people waking up early which can be a challenge and a reason for skipping workouts.

Working out just before the two other meals conserve some of the benefits of the morning workout. Admitting that you have reduced your calories intake, you should be almost hungry at that time. So, you are likely to burn more fat.

Another benefit, if you are are not too sedentary, is that your muscles are already awake and you will not need to warm up a lot.

If your job involves a lot of mental activity, you cannot do your work properly just after a workout session. However, you can jump to a meal just after a workout. So putting the meal between the workout and your work will save you time.

It was easy for me to stick to this schedule. I just don't allow myself to eat my lunch before finishing enough exercise. I sometimes bring my lunch in the gym, and I look at it as I exercise. So it's like a reward after the workout.

I think first and foremost is doing it when it's convenient and repeatable. If you can hit the gym at lunch every day, noon is best. If you're a night owl, after work. If you are an early bird, before work.

The only time I've seen being really bad is right before bed. Sometimes you just get too amped up to sleep.